Collapsible building drum



H. C. HODGKINS COLLAPSIBLE BUILDING DRUM Oct; 20, 1953 Filed Sept. 21, 1951` Oct. 20, 1953 H. c. HoDGKlNs 2,655,977

l COLLAPSIBLE BUILDING DRUM Filed sept. 21, 1951 e sheets-sheet 2 J7 fff/ 0a. zo, 1953 H. HD'GKINS 2,655,977

CQLLAPSIBLE BUILDING DRUM E?? 4 4. y INVENToR.

A Hau/J c. ,waff/Mr Y 7/ 'BY AGENT Oct. 20, 1953 H. c. HoDGKlNs COLLAPSIBLE BUILDING DRUM Filed Sept. 21, 1 951 Oct. 20, 1953 H.v c. HoDGKlNs v v2,655,977

COLLAPSIBLE BUILDING DRUM Filed Sept. 21* 1951 6 Shee's--Sheeil 5 ffy- .2.3

l -INVENTOR- A l l 'V f azz/1' Patented Oct. 20, 1953 UNITED STATE-.S` PATENT OFFICE 2,655,977y coLLArsIeLs. BUILDINGy oauM.

Hollis'C; Hodgkins, Chippewa. Falls, wismassignor to United States Rubber Company, Newy York, N; Y., a corporation of New Jersey Application September 21, 1951,. Serial No,2 .4'7.6&

Claims'. I

invention relates to. an improved build: ing drum. and more particularly it relates. to. an improved building drum,V fory making pneumatic tires, barrels, or other generally annular articles, that. can be collapsed rapidly to a compact formY for reilllival of the article.-

Increase. in cruising speed and the. desire. to. improve the riding ease and; comfort of the present day automobile have led to a demand tor more uniform tires than. those that have been considered adequate in. the, past.. Since the uniformity of a tire depends in large. measure upon. theV accuracy and precision. with. which the oar.- cassis. built, there. arises also a. concomitant domand. f0.1? a tire, building drum built to precision standards, and capable ofl retaining its accuracy throughout a reasonable period off use.

Accordingly, it is a principal object of the present. invention to provide a collapsible building drum for making tires and the like, having, an improved expanding and collapsing mechanism that accurately positions the working surfaces ofthe drum. I

Another object is the provision of a buildingdrum that retains its accuracy over a. prolonged period of service.

Still another object is to provide a drum expanding and collapsing mechanism that is essentially unaffected by rotation of the drum.

A further object of the invention is the provision of a building drum in which the workingsurfaces. are securely maintained in operative position, but yet may be rapidly collapsed when desired.

Still a further object is the provision ofV a co1- lapsibl'e building drum that expands and contracts With a minimum of weary and strain on the collapsing mechanism.

An additional object of the invention is to provide a drum collapsingmechanism which is especially adaptable to symmetrical construction of the various parts, so that the parts may loe readily interchanged or replaced.

It is another object to prov-ide a drum collapsing mechanism that is adapted to accommodate drum segments or working surf-aces ofvarious sizes and shapes, so that the diameter or shape of the building surface of the drum may be varied as desired within definite limits.

The manner in which the invention accomplishes the foregoing objects, as well as additional objects and advantages, will be made manifest in the following detailed description oi the invent-ion, which is intended to be read with reference to the accompanying drawings, wherein Eigt is a front elevational View of a col-.laps ible. tire. building drum of the invention in the expanded. position;

Fig. 2n is a side elevational View of the drum talgen, in section substantially along the line 2-2 of Fig. 1, with parts broken away;

Fig.v 3 is a front elevational View of' the drum in. the collapsed position?,

Fig.V 4 is an axial plan view of ax portionl or the drum,y taken partly in section along line llof; Fig. 1, with parts broken away;

Eig. 5 is ya similar view ofv another portion of; the drum taken substantially along the line 5--5Y of.' Eis. 1:`

Eig. 6 iS a.. fragmentary rear elevational view of actuating cylinders within the drum. with parts shown outline;

Fig. 7 is aside elevational viewof the shown in Fig.. 6; A

Eig.. 8 is a side elevational View of a central hub of the drum assembly, with parts brokenk away and parts shown in outline;

Figs. 9 and 10 are similar Views of' the hubv shown in Figi. 8, viewed from the front end and rear end, respectively;-

Figs. 11 and 12 are side and front elevational Views, respectively, of a collar forming part oi*- the collapsing mechanism;

Figs. 13 and 1-4 are front and side elevational views, respectively', of a control yoke formingr part ofthe collapsing mechanism; and,

Figs. 15 and 16 are fragmentary front elevational Views ofthe drum in an expanded and col--A lapsed position, respectively, showing largerv Working surfaces substituted for the original Working surfaces.

According to the invention, a building drum is provided with a plurality of outer arcuate seg-- ments forming the building surface of the drum, which can be collapsed or expanded radially in. wardly or outwardly with respect to a central relatively fixed hub, by means of a radially aeting actuating means secured to the hub and to at least some of the segments. The hub of the drum is adapted to be attached to the shaft of the usual tire building machine which rotates the drum in either direction as the tire is assembled on the surface of the drum in accordance with conventional practice. After the tire carcass is b uilt up on the surface of the drum, the drum is collapsed to a compact form, permitting removal of the carcass without distortion or injury.

Referring to the drawings, the improvedv drum includes three arcuate key' segment assemblies l0, Il', l2 and three alternately disposed intermediate larger arcuate segment assemblies i3, I4, i5 which together define, when the drum is in the expanded position, an uninterrupted smooth circular building surface l5 formed by the outer arcuate surfaces of the segment assemblies. Each of the smaller or key segment assemblies i9, il, i2 is slidably mounted at its inneror under-side on one of the axially disposed segment supporting plates il, i8, it, and the larger or principal segment assemblies i3, l, l5 similarly are each slidably mounted on one of the axially disposed segment supporting plates 2d, 2 l, 22.

The segment supporting plates {1 22 serve for attachment of an expanding and contracting mechanism, to be described below, by which the segments are radially movably supported from a central generally circular hub member or shaft 23- (Fig. 2) axially disposed within the interior of the drum. Toward its inner end, that is, to-

ward the end of the drum adapted to be mounted on the end of a rotary shaft 2li extending from the usual tire building machine (not shown), the central hub 23 has a section 25 of reduced diameter, over which there is iitted a surrounding attaching collar 25, rigidly secured to the hub 23 by means of bolts 2 passing through the collar 25 into a portion 28 of the hub 23 of larger diameter. at 29, to the attaching collar 23. The attaching collar 25 is adapted to be detachably secured to the end of the building machine 2e by suitable means, such as studs or bolts (not shown) or by an arrangement such as shown in my copending application Serial No. 146,312, filed February 25, 1950, now Patent No. 2,583,850, dated January 29, 1952, assigned to the same assignee as the present application, whereby the drum is readily mounted on or dismounted from the building machine shaft, as desired.

The circular portion 28 of the hub 23 is of reduced diameter compared to the central portion 30 of the hub, and a similarly reduced circular portion 3l, spaced from the portion 2S, is provided at the front or outer end of the hub. The hub portions 28 and 3l accommodate inner and outer spaced rotary collar members 32 and 33 respectively. As indicated most clearly in Figs. 1l and 12, the collar 32 has a circular central opening 34 for rotatably mounting the collar on the reduced portion 28 of the hub. Three radial arms 35, 36, 31 extend outwardly from the collar to form a spider-like arrangement. The arms are canted or biased somewhat in a clockwise direction as viewed in Figs. l and 12, and each arm is forked towards its outer end and is provided with axial openings 38, 32, d@ therethrough for accommodating portions of the expanding and collapsing linkage that will be described below. To limit the rotation of the spider or collar 32 with respect to the hub in such manner as to positively locate the collar 32 at a definite position when the drum is in the expanded operative condition, a radially aligned, rigidly secured stop di projects axially from one face of the collar. The spider or collar 32 is mounted on the reduced inner portion 28 of the hub 23 with this projecting stop lil projecting toward the central enlarged portion 30 of the hub, and the stop il is so spaced from the central axis of the assembly as to engage a cooperating projecting stop 42 fixed to the periphery of the enlarged portion Si) of the hub 23 at the inner end thereof. The stop 62 has a radially aligned face 43' designed to meet one face M of the stop il on the collar 32, and is so positioned as to positively The hub 23 is also keyed, asv

site end of the enlarged portion 39 of the hub 2,3, in a manner analogous to the stop ft2, so as to position the outer rotary collar or spider 33 in the same manner as described in connection with the inner collar 32.

For securing the various segment supporting plates il-22 to the inner and outer rotary collars or spiders 32, 3,5 which guide the segments in their expanding and collapsing movement, there are provided, on each of the arms 35, 35, 3l of the inner spider 32, generally V- shaped control links or yokes P22, 5i pivotally secured thereon by pivot pins 52, 5:3 passing through the joint or apex of the V and through the respective openings 38, te, lil toward the outer ends of the spider arms. Similarly, outer control yokes 55, 56, 57 are pivotally mounted by means of pivot pins 58, 59, 5d on the end of the arms 55, 45, il of the outer collar or spider 33. Each control yoke liS--EL -5'3 includes an outwardly extending forked arm 5 l-Sii and an outwardly extending single arm 2?-72 Which carry at their ends pivotal attachments to the various segments supporting plates i-22 in such manner that each plate is pivotally secured toward one end to a forked arm of a control yoke and toward the other end to a single arm of a control yoke. Thus, forked arms 6i, t2, 23 of the control yokes d2, 50, 5I carried by the inner spider 32, are pivotally attached by means of intermediate pivotal tie links 73, T4, i5, respectively, to brackets '15, il, 78 which extend laterally from the key segment supporting plates il', le, is toward the axially inner end thereof. The opposed single arms 6l, 68, 69 of these yoke-s are pivotally secured to brackets l, 30, 8i which extend laterally from the larger segment supporting plates 20, 2l, 22 toward the axially inner end thereof. In this way, the control yokes ed, 5e, 5i serve to connect the key segments and the larger segments to each other toward their axial inner end to control the motion of the two groups of segments in a manner that will be described in detail below.

In an analogous manner, the two sets of segments are connected together toward their axially outer end, and also connected to the front spider 33, by the front control yokes 55, 5B, 5l. Thus, the forked arms Eli, 65, 66 of the front yokes 55, 5B, 5l carry pivotal tie links 82, 23, 36 that are pivotally attached to brackets E55, 85, el extending laterally from the key segment supporting plates il, i8, I9 toward the outer or front end thereof, while the single arms le, 'i l2 of these yokes are pivotally attached to d8, 39, 96 of the larger segment supporting plates Eil, 2i, 22 toward the front end thereof.

The inner or rear yokes 49, 55, 5| thereby bridge from the key segments to the larger segments at the rear of the drum, while the outer or front yokes 55, 56, 5l bridge from the key segments to the larger segments at the front of the drum, m a similar manner, but in an opposite sense, by reason of the reverse disposition of the front airihd rear spiders and yokes, compared to each o er.

In assembly, the reary or inner collar or spider 32 -is maintained in its position and restrained against axial movement on the reduced portion 23 of the hub 23 between the mounting collar 2S and the enlarged portion 39 of the hub by the bolts 2l, while the outer or front collar or spider 33 is maintained in position and restrained against axial movement between the enlarged portion 3s of the hub and an outer retaining plate 9| that is held in place by means of bolts 92 passing through the retaining plate into the front face -of the reduced portion 3| of the hub.

For imparting the desired radial collapsing and expanding motion to the segments, there are provided three radially disposed fluid-operated actuating cylinders IBS, IBI, |82 that are mounted in radially disposed axially spaced bores |03, |04, I5 passing through the enlarged portion 3i! of the hub 23 along radial planes disposed at an angle of 120 to each other. The operating cylinders |63, lill, |62 are connected to the key segment supporting plates I8, ll, I9, respectively, by means of piston rods |66, le?, |98 extending from the front end of the cylinders. At their outer ends, the piston rods are fitted into suitably drilled holes |99 or IIB in the segment supporting plates, wherein they are secured by a screw III. The bores H33, IQ, |95 in which the cylinders |09, IUI, |02 are disposed, are counterbored at one end to a larger diameter so that they snugly accommodate enlarged front end caps I I2, H3, I I4 of the cylinders, with the outer face of such caps flush with the outer surface of the enlarged portion 32 of the hub 23, and each cylinder is maintained firmly in place within the hub by means of a keeper, such as keeper I |5, secured in place by a screw I6, passing into the hub.

To actuate the operating cylinders in such manner as to draw the piston rods and segment assemblies inwardly radially to collapse the drum, there is provided at the center of the inner end face of the hub 23 in engagement with the face of the machine shaft 24, a iluid supply opening II'I that is in communication with a central axial fluid supply line IIS within the hub 24, and that leads to internal fluid passageways H9 that pass through the hub and lead into the respective front caps IIZ-I i4 of the various cylinders IBB-|62 At each cylinder a connecting elbow, such as elbow |22, carried by the cylinder end cap, is disposed within a milled Slot on the surface of the enlarged portion of the hub, such as slot |2l, and is therein maintained firmly in place against an opening, such as opening |22, from the passageway I I9 by the keeper l I5. Fluid supplied to the front end of the cylinders in this manner actuates a piston (not shown) within each cylinderl to produce a collapsing movement. For actuating the cylinders in a radially outward direction to expand the drum there is provided an additional opening |23 in the inner end face of the hub that is supplied with actuating fluid from an annular passageway |215 passing axially within the hub 2li, and leading to a passageway |25 that extends axially and radially through the hub into communication with a distributing block |25 that is secured at the surface of the enlarged portion Sil of the hub. The distributing block |26 serves to distribute the actuating fluid to three external fluid lines I2?, |23, |29 leading to rear end caps I3, ISI, |32 of the cylinders |69, lill, H52. Fluid supplied to the rear end of the cylinders in this manner actuates the piston rods and segment assemblies outwardly simultaneously for the expanding movement. It will be understood .that application of fluid pressure to the supply passageways I.I8, |24 within 'the hub 24 is controlled by the usual control valve (not shown), and that the various passageways serve either as inlets orl outlets for the actuating fluid, to either expand or collapse the drum, depending on the position of the control valve.

To further guide and steady the principal segment assemblies I3, I4, I5 in their radial expanding and collapsing movement, there is associated with each of these segments a telescoping guide arrangement extending from the hub to the supporting plates of the segments. The telescoping guides for the segment assemblies I4 and. I5 include radially extending guide studs |35, I 36 rigidly fitted into holes |31, I 38 drilled into plane faces |39, I4@ on the enlarged portion 32 of the hub 23 toward the axially outer end thereof. Toward their radially outer ends the guide studs it, |25 extend slidably into radial bearing sleeves MI, |2 that are secured at their outer ends into a recess on the underside of the segnient supporting plate, such as recess |43 on the inner surface of the segment supporting plate 22 of the segment assembly I5, as by screws |44 passing through holes |45 disposed around the periphery of the recess |133, into a mounting flange at the base of the sleeve. The remaining large segment assembly i3 similarly has a guide sleeve |48 extending radially inwardly from the inner surface of its supporting plate 26, and slidably interntted with a similar radial guide stud |659 rigidly tted at its inner end into a radial hole I5@ drilled in a plane surface |5I of the enlarged portiony Sil of the hub 23, toward the axially inner end thereof.

The portions of the segment assemblies which define the building surface i6 of the drum include segment halves, such as halves |55, 55 of the key segment Ill, and halves |51, |58 of larger segment I5, disposed toward either side of a circumferential center line ofthe building surface. At their outer marginal edges the segment halves are so undercut and shaped as to provide for the desired shaping of the bead area of the tire as it is built up on the drum. The segment halves are slidably mounted for adjusting movement in an axial direction on the respective supporting plates of the various segments. For this purpose, inwardly extending portions of the segment halves are provided with undercut recesses or slots, such as slots |59, IEil of segment halves |55, |51, into which extend slidably cooperating projections of the segment supporting plates, such as projections IBI, |52 of the supporting plates l'i, 22. The segment halves may be securely positioned at a desired distance from the circumferential center line of the building surface by tightening tapered screws extending into slotted ends of the segment supporting plates, such as screw |63 threaded through slotted end portion |62 of the segment supporting plate Il. As the tapered screw is turned into the slotted portion, the segment supporting plate is caused to expand outwardly, thereby tightening the projecting guide of the supporting plate in the sliding slot of the segment half.

The inner edge of each segment half is proof spacer pieces, such as lip |66 of spacer piece |51, that can be interposed between the segment halves along the circumferential center line of the drum for the purpose of varying the width of the building surface. The spacer pieces have the same arcuate length as the segment into which they are adapted to nt, and they may have various widths, depending on the desired width of the drum working surface. The outer surface of the spacer pieces is flush with the outer surface of the segment halves when in position, and the inner surface of the spacer piece is provided with spaced radial holes, for receiving guide pins, such as pin E52, that extend outwardly radially from the segment supporting plates at spaced intervals along the circumferential center line of the drum, to serve as a guide in positioning the spacer pieces in place.

The inner surface of the supporting plates of the larger segment assemblies, such as plate 22, is also provided with recesses, such as recesses |73, I'l which are adapted to receive projecting portions of the rear end caps of the operating cylinders in radial alignment therewith, when the drum is in the collapsed position, such as projection |72 from the end cap I3I of the central cylinder Ill.

The operation of the expanding and collapsing mechanism will now be described. To collapse the drum, fluid pressure is applied to the front ends of the operating cylinders Idil, 52|, 82 from the fluid supply line IIS within the shaft 2li of the building machine, into the central opening Il? in the end faceof the hub 23 of the drum and through internal passageways I I 3 within the hub. This causes the piston rods 1S", It?, |38 and attached key segment supporting plates I'l, i8, I3 to move inwardly, thereby moving the key segment assemblies I3, II, I2 radially inwardly simultaneously. The inward movement of the key segment assemblies causes, through the small pivotal tie links "i3, 14, 75 a clockwise tilting of the rear control yokes 49, 59, 5I about their pivotal connections 52, 53, 54 to the arms of the rear rotary collar or spider 32, accompanied by a simultaneous counter-clockwise tilting, through connecting pivotal tie links 82, B3, Si of the front control yokes 55, 5S, 51 about their pivotal connections 58, t9, te to the arms of the front spider 33. The inward movement of the front and rear sets of small pivotal tie links in the respective directions stated is a consequence of the fact that the connection of the tie links to the segments is radially offset in the stated direction with respect to the connection of the tie links to their respective contre-l yoke Such tilting of the front and rear control yokes causes, through the arms '5l-'l2 or the yokes pivotally attached to the supporting plates 2Q, 2 I, 22 an inward movement of the large segment assemblies I3, Iii, I5. As the large segment assemblies move radially inwardly after the key segment assemblies, their motion is guided and controlled by the rotation of the front and rear spiders 33, 32 about the central hub 23 of the drum. The rear spider 32 is caused to rotate in a clockwise direction by the collapsing movement while the front spider 33 is caused to rotate in a counter-clockwise direction. The large segment assemblies are further guided and steadied on a purely radial path during the collapsing movement by their respective guide sleeves II, M2, |48 sliding on the various radial guide studs |35, |36, |49 extending radially from the hub 23. In the final collapsed position the drum assumes a compact form with 8 the key segment assemblies Il), II, I2 drawn close to the hub 23 and nested within the large segment assemblies I3, I4, I5 which are drawn thereover.

The expanding operation is the reverse of the foregoing. Fluid pressure for the expanding movement is supplied from the annular passageway |24 within the machine shaft 2Q to the opening |23 in the end face of the hub 23 and into the internal passageway |25 passing through the hub 23 to the distributor block |26, and thence through external lines |21, I 28, E23 to the rear ends of the operating cylinders I G, IBI, |02. This causes the piston rods HB5, |01, I and attached segment supporting plates I l, I8, I9 to move radially outwardly. The resulting outward movement of the key segment assemblies I3, II, I2 causes, through the rear small pivotal tie links '53, lli, 'l5 and the iront tie links 82, 83, 6d a tilting movement of the rear control yokes 49, 5I), 5I and of the front control yokes 55, 53, 5"! in a reverse direction compared to the tilting that took place during the collapsing movement. The tilting movement of the control yokes communicates to the large segment assemblies I3, I, i5 an outward radial movement, while the inner and outer rotary spiders or collars 32, 33 rotate about the hub 23 in a reverse direction compared to the rotation that took place during the expanding movement.

As the segments approach the expanded position, the centers of the pivotal connections 52-54 and 33--60 of the spider arms to the control yokes pass over-center or by-oenter with respect to a center line drawn from the axis of the drum through the center of the pivotal connection between the control yokes and the supporting plates 2G, 2 i, 22 of the larger segment assemblies. Shortly after the spiders thus travel over-centers the stops on the spiders, such as stop lII contact the fixed stops 42, i8 on the hub 23, and the various segments are thereby denitely positioned in the nal expanded condition. Because the pivotal connection of the spiders to the control yokes has moved over-center immediately before the spiders have contacted their respective stops, the segments become firmly locked in place. As a result of the over-center travel of this pivotal point, the initial collapsing movement of the key segments l0, II, I2 does not immediately produce collapsing movement of the larger segments I3, I4, I5, since the larger segments do not move inwardly on the collapsing cycle until the spiders 32, 33 move away from their stops for a distance equal to the by-center travel that took place at the end of the expanding cycle. This delayed movement of the larger segment assemblies with respect to the key segment assemblies, allows the key segments to move clear before the larger segments start their collapsing movement. By this arrangement, segment halves with comparatively deeply radially extending portions may be mounted on the segment supporting plates, for building tires or other objects with radially extending portions at their marginal edges, without interference of the segments during the collapsing cycle. The arrangement described permits an unusually high degree of collapse, that is, the disparity between the expanded diameter of the drum and the collapsed diameter is greater than is usual with conventional types of drum. 'I'he compactness of the collapse made possible with the present drum also makes it feasible to vary the external diameter of the building drum, or the shape of the working surfaces of the drum.

9 to a greater extent than has heretofore been considered practicable. Thus, referring to Figs. l and 16, the original segmentsVsuch as segments I2 and I5 (Fig. 1\),7may be replaced by segment members |75 and I'IB, the outer surfaces of which are spaced a greater radial distance from the center of the drum than were the working surfaces of the original Segments I2 and I5, thereby constituting a building drum of larger diameter without any necessity for changing the collapsing mechanism per se. The new segments I'I5 and I'I6 have correspondingly larger supporting portions lI'I'I and |18, respectively, which are slidably mounted on their respective supporting plates I9 and 22, in the same manner that the original smaller segments I2 Xand l5 were munted thereon. In the collapsed position, shown in Fig. 16, the segments overlap in a compact arrangement without interference with i each other. y

Because the collapsingvmechanism described provides for purely radial rectilinear collapsing motion of the segments, the present drum is particularly adapted for forming objects, such as rubber barrels or the like, having internal ribs running lengthwise or circumferentially, and there is no diinculty about collapsing the drum and removing such objects without distortion or injury to the product. i

It is also important to note that the invention provides, during the collapsing and expanding movement of the segments, radial guides for the key segments in the form of the radial actuating cylinders, and radial guides for the larger segments in the form of the radial telescoping stud and sleeve arrangements. Such radial guiding means play little or no part as a driving medium between the hub and the segments as the drum rotates on the machine shaft, since the pivotal guide linkages in the form of the rotary spiders and tilting control yokes transmit essentially all of the rotating driving force. Therefore, the rotation of the drum, and sudden starting and stopping of the drum, or sudden reverse rotation of the drum, have substantially no tendency to distort or displace the radial guides for the segments. Hence, the drum remains true and accurate with respect to its expanding and collapsing movement even after comparatively long periods of use.

Another advantage of the construction shown is that each segment is attached to adjacent segments at supporting points diagonally spaced toward opposite ends of the segments. Because of this arrangement, each segment is effectively connected to the adjacent segment on either side of it, so that no one segment can contract or expand without the adjacent segment doing likewise. Another advantage of this arrangement is that the various parts may be made alike, that is, there need be no right-hand and lefthand parts, and corresponding parts are always inter-changeable.

Since the expanding and collapsing movement is effected by three separate radial cylinders, each attached directly to one of the key segments, movement of the segments is directly effected in a rapid and positive manner with a comparatively small amount of power and with a minimum of wear and strain on the collapsing mechanism. This arrangement permits a most compact collapse, and it will also be seen that the expanding and contracting motion is entirely independent of any rotary motion of the drum, so that starting, stopping, and reversal of rota- 10 tion of the ldrum have no tendency to cause undesired collapse of the segments.

'I'he stops providedon the rotary spiders and hub provide for rigid locking of the drum in the expanded position. `These stops are so located at the pivotal connection between the spider arms and the control yokes travels by-center toward the vend of the expanding movement, with the result that thehlarger segments actually move inwardly a small amount at the end of the expandingk cycle, vcausing them toY bear nrrnly against the key segments, which lare being urged outwardlyby the actuating cylinders. Therefore, while the spider stops rest against the hub stops nopartofV` the collapsing mechanism can move, with the result that thadrum rotatesas a rmly rigidunit with noside thrustvo'r strain on opereiigllnlegf Qf iiwllepsns unit- For this reason., @sdram is .enabled i0 maintain. itsefx- Dended position with, ,unusual acuracy, vreveil, after the drum has been in use for comparatively long periodswof time. A i i y u W Having thus described my invention, what I claim and desire to protect by Letters Patent is:

ALA collapsible building drum comprising in combination a plurality `of arcuate segments dening `a circular building surface, a central axial supporting hub within said segments, and

radially extending actuating means movable in a purely radial direction attached between said segments andcsaid hub for collapsing and expanding said segments.l a y 2. A collapsible building drum comprising in cijmbination a plurality of arcuate segments dinne: a circular building surfacaa central axial supporting hub within Lsaid segments, and

radially extending uid actuated cylinders atta'clied between said segments and said hub for collapsing and expanding said segments.

3. A collapsible building drum comprising in combination a plurality of arcuate segments defining a` circular building surface, a central axial supporting hub Within said segments, radially extending actuating means movable in a purely radial direction attached to some of said segments and said hub for collapsing and expanding said some segments, and pivotal linkages connecting said some segments to the remaining segments for collapsing and expanding the remaining segments.

4. A collapsible building drum comprising in combination a plurality of arcuate segments defining a circular building surface, a central axial supporting hub within said segments, radially extending uid actuating cylinders attached to some of said segments and said hub for collapsing and expanding said some segments, and pivotal linkages connecting said some segments to the remaining segments for collapsing and expanding the remaining segments.

5. A collapsible building drum comprising in combination a plurality of arcuate segments defining a circular building surface, a central axial supporting hub within said segments, radially extending actuating means movable in a purely radial direction attached to some of said segments and to said hub for collapsing and expanding said some segments, pivotal linkages connecting said some segments to the remaining segments for collapsing and expanding the remaining segments, and radially telescoping guides attached between the remaining segments and the hub for limiting the collapsing and expanding movement of said remaining segments to purely radial movement.

6. A collapsible building drum comprising in combination a VVplurality of arcuate segments defining a circular building surface, a central axial supporting hub within said segments, radially extending actuating Ymeans movable in a purely radial direction attached to some of said segments and to said hub for collapsing and expanding said some segments, pivotal linkages connecting said some segments to the remaining segments for collapsing and expanding the remaining segments, rotary collars mounted on Said hub, said pivotal links being pivotally connected to said rotary collars for guiding the collapsing movement of said remaining segments.

7. A collapsible building drum comprising inv combination a set of arcuate key segments, a set of alternately disposed arcuate larger segments, a central axial supporting hub within said segments, and a radially extending uid actuated cylinder attached between each segment of one of said sets of segments and the hub for collapsing and expanding said segments. l

8. A collapsible building drum comprising in combination a set of arcuate key segments, a set of alternately disposed arcuate larger segments, a central axial supporting hub within said segments, a radially extending fluid actuated cylinder attached between each of said key segments and said hub for collapsing and expanding said key segments, and pivotal linkages connecting said key segments to said larger segments for collapsing and expanding said larger segments with said key segments.

9. A collapsible building drum comprising in combination a set of arcuate key segments, a set of alternately disposed arcuate larger segments, a central axial supporting hub within said segments, a radially extending uid actuated cylinder attached between said key segments and 12 said hubofor ollapsingand expanding said`key segments, pivotal linkages connecting said key segments to said larger segments for collapsing and expanding said larger segments with said key segments, rotating guiding means mounted on said hub, said pivotal linkages being pivotally attached to said rotating guiding means to guide the collapsing, and expanding movement of said larger segments. A

10. A collapsible building drum comprising in combination a set of arcuate key segments, a set of alternately disposed arcuate larger segments, a central axial supporting hub within said segments, a radially extending fluid actuated cylinder attached between said key segments and said hub for collapsing and expanding said key segments, pivotal linkages between said key segments and said larger segments for collapsing and expanding said larger segments, rotary guiding means mounted on said hub, said pivotal linkages being pivotally joined to said rotary guiding means for controlling the collapsing and expanding movement of said larger segments, and radially telescoping `guide means attached between said larger segments and said hub.

HOLLIS C. HODGKINS.

References Cited in the lleV of this patent UNITEDV STATES PATENTS Number Name Date 924,036 Burgess June 8, 1909 1,140,771 Schur May 25, 1915 1,275,790 Taylor f Aug. 13, 1918 1,434,567 Smith et a1. Nov. 7, 1922 l1,454,995 Denmire May 15, 1923 1,877,746 Heston et al Sept. 13, 1932 2,201,469 Bostwick May 2l, 1940 

